Female common marmoset monkey reproductive capacity is completely regulated by social status. Subordinate females show no ovarian activity and have low levels of pituitary gonadotropins, yet hypothalamic gonadotropin-releasing hormone (GnRH) output is not different when compared to cycling dominant females. The present study will systematically examine neuroendocrine parameters at several points along the hypothalamic-pituitary-gonadal axis in order to characterize any subtle differences between social states. Results will identify mechanisms by which psychosocial factors can influence reproductive integrity through small variations, rather than dramatic global changes, in the neuroendocrine environment. In all studies GnRH and luteinizing hormone (LH) parameters will be measured and compared between dominant, rank 2 and rank 3 females. Females will undergo push-pull perfusion of the stalk-median eminence with concomitant blood sampling at 10 min intervals for up to 10 hr. Experiment 1 will look for altered diurnal patterns hypothalamic GnRH and pituitary LH release. Experiment 2 will characterize GnRH and LH responses underlying the ability or inability to generate an ovulatory LH surge in response to estradiol. Experiment 3 will examine differential pituitary stimulation and responsiveness to standardized GnRH challenges; GnRH receptor concentrations will be quantified.